Method of driving optical device, optical system, and display

ABSTRACT

A method of driving an optical device is provided. The optical device including an optical member, a first actuator which displaces the optical member around a first axis, and a second actuator which displaces the optical member around a second axis perpendicular to the first axis. The method including exciting the first actuator by inputting a first drive signal to the first actuator, exciting the second actuator by inputting a second drive signal to the second actuator, and setting a value of the second drive signal to a value for substantially stopping exciting the second actuator in a period of the exciting the first actuator.

The present application is based on, and claims priority from JPApplication Serial Number 2020-193280, filed Nov. 20, 2020, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a method of driving an optical device,an optical system, and a display.

2. Related Art

In the past, there has been known a display which oscillates an opticalmember to shift a light path of image light entering the optical memberto thereby increase the resolution. For example, in JP-A-2020-091343(Document 1), a glass plate is oscillated by two actuators to perform alight path shifting action of shifting the light path of the imagelight. According to this configuration, by moving a single pixel to fourpositions of positions P1, P2, P3, and P4, four pixels smaller in sizethan the single pixel are apparently displayed.

In the configuration described in Document 1, alight path shiftingaction in which oscillations of the glass plate are combined with eachother is performed in accordance with drive signals to be supplied to afirst actuator and a second actuator. In this configuration, sincevoltages are applied to the two actuators, there is a problem that thepower consumption is high.

SUMMARY

An aspect of the present application example is directed to a method ofdriving an optical device including an optical member having an opticalarea which has a rectangular shape in a plan view, and which lightenters, a first actuator configured to displace the optical memberaround a first axis which passes through a center of the optical area inthe plan view, and which forms an angle smaller than 90° with a firstside of the optical area, and a second actuator configured to displacethe optical member around a second axis which passes through the centerof the optical area, and which is perpendicular to the first axis. Themethod includes inputting a first drive signal into the first actuatorto thereby excite the first actuator, inputting a second drive signalinto the second actuator to thereby excite the second actuator, andsetting a value of the second drive signal to a value for substantiallystopping exciting the second actuator in a period of exciting the firstactuator.

Another aspect of the present application example is directed to anoptical system including an optical device including an optical memberhaving an optical area which has a rectangular shape in a plan view, andwhich light enters, a first actuator configured to displace the opticalmember around a first axis which passes through a center of the opticalarea in the plan view, and which forms an angle smaller than 90° with afirst side of the optical area, and a second actuator configured todisplace the optical member around a second axis which passes throughthe center of the optical area, and which is perpendicular to the firstaxis, and a drive circuit, wherein the drive circuit performs outputtinga first drive signal to the first actuator to thereby excite the firstactuator, outputting a second drive signal to the second actuator tothereby excite the second actuator, and setting a value of the seconddrive signal to a value for substantially stopping exciting the secondactuator in a period of exciting the first actuator.

Another aspect of the present application example is directed to adisplay including a light source, a light modulator configured tomodulate light emitted from the light source, an optical deviceincluding an optical member having an optical area which has arectangular shape in a plan view, and which the light modulated by thelight modulator enters, a first actuator configured to displace theoptical member around a first axis which passes through a center of theoptical area in the plan view, and which forms an angle smaller than 90°with a first side of the optical area, and a second actuator configuredto displace the optical member around a second axis which passes throughthe center of the optical area, and which is perpendicular to the firstaxis, a drive circuit, and an optical system configured to transmit thelight transmitted through the optical device, wherein the drive circuitperforms outputting a first drive signal to the first actuator tothereby excite the first actuator, outputting a second drive signal tothe second actuator to thereby excite the second actuator, and setting avalue of the second drive signal to a value for substantially stoppingexciting the second actuator in a period of exciting the first actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing an optical configuration of aprojector according to a first embodiment.

FIG. 2 is an explanatory diagram showing a light path shift by a lightpath shifting device.

FIG. 3 is a functional block diagram of the projector.

FIG. 4 is a plan view showing a configuration of a liquid crystaldisplay element.

FIG. 5 is a plan view of the light path shifting device.

FIG. 6 is a partial cross-sectional view of the light path shiftingdevice.

FIG. 7 is a partial enlarged cross-sectional view of the light pathshifting device.

FIG. 8 is an explanatory diagram showing a relative position between alight modulator and the light path shifting device.

FIGS. 9A to 9C are timing charts showing waveforms of drive signals andchanges of a position of a pixel.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT 1. Overall Configuration ofProjector

An exemplary embodiment of the present disclosure will hereinafter bedescribed with reference to the drawings.

FIG. 1 is an explanatory diagram showing an optical configuration of aprojector 1 as an example of a display according to the presentembodiment.

The projector 1 is provided with a light source 102 and a lightmodulator 108 for modulating the light emitted by the light source 102based on an image signal input from the outside, and projects aprojection image 101A on a screen 101. As the light modulator of theprojector 1, there can be used an LCD (Liquid Crystal Display), adigital micromirror device (DMD), and so on. In the present embodiment,the projector 1 provided with liquid crystal display elements 108R,108G, and 108B as the light modulator 108 will be described as anexample.

The projector 1 is provided with mirrors 104 a, 104 b, and 104 c,dichroic mirrors 106 a, 106 b, a dichroic prism 110, a light pathshifting device 2, and a projection optical system 112.

As the light source 102, there can be cited, for example, a halogenlamp, a mercury lamp, a light emitting diode (LED), and a laser source.Further, as the light source 102, there is used a device for emittingwhite light. The light emitted from the light source 102 is separatedby, for example, the dichroic mirror 106 a into red light (R) and therest of the light. The red light is reflected by the mirror 104 a, andthen enters the liquid crystal display element 108R, and the rest of thelight is further separated by the dichroic mirror 106 b into green light(G) and blue light (B). The green light enters the liquid crystaldisplay element 108G, and the blue light is reflected by the mirrors 104b, 104 c, and then enters the liquid crystal display element 108B. Thedichroic mirrors 106 a, 106 b correspond to a spectral element forseparating the light emitted by the light source 102 into the red light(R), the green light (G), and the blue light (B).

The liquid crystal display elements 108R, 108G, and 108B aretransmissive spatial light modulators corresponding respectively toprimary colors of R, G, and B. The liquid crystal display elements 108R,108G, and 108B each have a liquid crystal panel provided with pixelsarranged in, for example, a 1080×1920 matrix. In each of the pixels, thelight intensity of the transmitted light with respect to the incidentlight is controlled, and in each of the liquid crystal display elements108R, 108G, and 108B, the light intensity distribution of all of thepixels is controlled in a coordinated manner. The light beams spatiallymodulated by such liquid crystal display elements 108R, 108G, and 108Bare combined with each other by the dichroic prism 110, and full-colorimage light LL is emitted from the dichroic prism 110. Then, the imagelight LL thus emitted is projected on the screen 101 in an enlargedmanner by the projection optical system 112. The projection opticalsystem 112 corresponds to an example of an optical system.

The projection optical system 112 projects the light modulated by theliquid crystal display elements 108R, 108G, and 108B on the screen 101to form the projection image 101A on the screen 101. An action of theprojector 1 forming the projection image 101A corresponds to performingdisplay.

The projection optical system 112 is provided with at least one lens.The projection optical system 112 can also be an optical system providedwith at least one or more mirrors, or can also be an optical systemprovided with one or more lenses and one or more mirrors. The projectionoptical system 112 can be provided with a mechanism for adjusting thefocus on the screen 101.

The light path shifting device 2 is disposed between the dichroic prism110 and the projection optical system 112. It is possible for theprojector 1 to display an image higher in resolution than the liquidcrystal display elements 108R, 108G, and 108B on the screen 101 byperforming a shift of the light path of the image light LL using thelight path shifting device 2, namely a so-called light path shift. Forexample, when using the liquid crystal display elements 108R, 108G, 108Bcompatible with the full high definition of displaying an image in1920×1080 pixels as described above, it is possible to display an imagecompatible with the 4K resolution on the screen 101. The light pathshifting device 2 corresponds to an example of an optical device.

2. Aspect of Light Path Shift

The high resolution achieved by the light path shift will be describedwith reference to FIG. 2 .

FIG. 2 is an explanatory diagram showing the light path shift by thelight path shifting device 2. As described later, the light pathshifting device 2 has a glass plate 30 as a light transmissive opticalmember for transmitting the image light LL. The light path shiftingdevice 2 changes the posture of the glass plate 30 to thereby shift thelight path of the image light LL using the refraction of light.

In FIG. 2 , there are shown an X axis and a Y axis perpendicular to eachother. The X axis and the Y axis correspond to arrangement directions ofthe pixels in a display area of each of the liquid crystal displayelements 108R, 108G, and 108B. For example, the liquid crystal displayelements 108R, 108G, and 108B each have 1920 pixels along the X axis,and 1080 pixels along the Y axis. The X axis and the Y axis correspondrespectively to a horizontal direction and a vertical direction of theprojection image 101A to be projected on the screen 101. Here, onedirection along the X axis is defined as an X+ direction, and theopposite direction is defined as an X− direction. Further, one directionalong the Y axis is defined as a Y+ direction, and the oppositedirection is defined as a Y− direction.

The position of the glass plate 30 in the state in which the light pathshifting device 2 does not displace the glass plate 30 is defined as areference position. At the reference position, the glass plate 30 isparallel to an X-Y plane. The light path shifting device 2 in thepresent embodiment oscillates the glass plate 30 to thereby guide theimage light LL to a predetermined position.

FIG. 2 schematically shows how the pixel Px included in the image lightLL transmitted through the glass plate 30 is shifted. The position ofthe pixel Px when the glass plate 30 is located at the referenceposition is defined as a position P0. A first position P1, a secondposition P2, a third position P3, and a fourth position P4 are each aposition to which the image light LL of the pixel Px is guided due tothe oscillation of the glass plate 30. For example, the first positionP1 is a position shifted toward the X+ direction and the Y+ direction asmuch as a half pixel with respect to the position P0. The secondposition P2 is a position shifted toward the X− direction and the Y−direction as much as a half pixel with respect to the position P0. Thethird position P3 is a position shifted toward the X− direction and theY+ direction as much as a half pixel with respect to the position P0,and the fourth position P4 is a position shifted toward the X+ directionand the Y− direction as much as a half pixel with respect to theposition P0. FIG. 2 corresponds to a diagram of the glass plate 30viewed from the dichroic prism 110.

The first position P1 corresponds to a third position, and the secondposition P2 corresponds to a fourth position. Conversely, it is possibleto adopt a configuration in which the first position P1 corresponds tothe fourth position, and the second position P2 corresponds to the thirdposition. The third position P3 corresponds to a first position, and thefourth position P4 corresponds to a second position. Conversely, it ispossible to adopt a configuration in which the third position P3corresponds to the second position, and the fourth position P4corresponds to the first position.

A first axis J1 and a second axis J2 shown in FIG. 2 are each an axis ofthe oscillation of the glass plate 30, and are each an imaginary axisline set in a mechanism with which the light path shifting device 2oscillates the glass plate 30.

At the reference position, the glass plate 30 is not tilted around thefirst axis J1 or the second axis J2.

The glass plate 30 is displaced around the first axis J1 due to theaction of a first actuator 6 described later. The directions of thedisplacement of the glass plate 30 are a normal direction and a reversedirection. The normal direction around the first axis J1 is a directionin which a portion at the X− side and the Y+ side of the glass plate 30is displaced frontward with respect to the X-Y plane. When the glassplate 30 is displaced toward the normal direction around the first axisJ1, the pixel Px moves in a third direction F3 toward the third positionP3. The reverse direction around the first axis J1 is a direction inwhich a portion at the X+ side and the Y− side of the glass plate 30 isdisplaced frontward with respect to the X-Y plane. When the glass plate30 is displaced toward the reverse direction around the first axis J1,the pixel Px moves in a fourth direction F4 toward the fourth positionP4. The third direction F3 and the fourth direction F4 are perpendicularto the first axis J1 and are opposite to each other.

The glass plate 30 is displaced around the second axis J2 due to theaction of a second actuator 7 described later. The directions of thedisplacement of the glass plate 30 are a normal direction and a reversedirection.

The normal direction around the second axis J2 is a direction in which aportion at the X− side and the Y− side of the glass plate 30 isdisplaced frontward with respect to the X-Y plane. When the glass plate30 is displaced toward the normal direction around the second axis J2,the pixel Px moves in a second direction F2 toward the second positionP2. The reverse direction around the second axis J2 is a direction inwhich a portion at the X+ side and the Y+ side of the glass plate 30 isdisplaced frontward with respect to the X-Y plane. When the glass plate30 is displaced toward the reverse direction around the second axis J2,the pixel Px moves in a first direction F1 toward the first position P1.The first direction F1 and the second direction F2 are perpendicular tothe second axis J2 and are opposite to each other.

The projector 1 performs the shifts of the light path in the firstdirection F1, the third direction F3, the second direction F2, and thefourth direction F4 in sequence to thereby increase the apparent numberof pixels, and thus, it is possible to achieve the high resolution ofthe projection image 101A to be projected on the screen 101. Forexample, the projector 1 displays an image PA at the first position P1,displays an image PB at the third position P3, displays an image PD atthe second position P2, and displays an image PC at the fourth positionP4 using the pixel Px. Due to the series of display, in the projectionimage 101A, the four images PA, PB, PD, and PC are displayed at the fourpositions shifted as much as a half pixel from each other with thesingle pixel Px. Thus, the projection image 101A is visually recognizedas an image higher in resolution constituted by pixels smaller than thepixel Px.

When displaying the projection image 101A with the frequency of 60 Hz asa whole, the projector 1 makes the liquid crystal display elementsperform the display at 240 Hz as a quad rate, and shift the pixel Px inaccordance with an update of the display. As shown in FIG. 2 , whenmaking the pixel Px perform the display in the order of the images PA,PB, PD, and PC, an action of moving the pixel Px in the first directionF1, an action of moving the pixel Px in the third direction F3, anaction of moving the pixel Px in the second direction F2, and an actionof moving the pixel Px in the fourth direction F4 are performed insequence.

The actions described above are illustrative only, and the shift amountof the pixel Px is not limited to a half pixel, but can also be, forexample, a fourth of length of the pixel Px, or three fourths thereof.Further, the diagram shows an example in which the pixel Px has a squareshape, but it is sufficient for the pixel Px to have a rectangularshape. In this case, the shift amount in the X axis of the pixel Px canbe set to, for example, a half or a fourth of the length of the side ofthe pixel Px parallel to the X axis. Further, the shift amount in the Yaxis of the pixel Px can be set to a half or a fourth of the length ofthe side of the pixel Px parallel to the Y axis.

3. Functional Configuration of Projector

FIG. 3 is a block diagram of the projector 1 shown in FIG. 1 . Theprojector 1 is provided with a control circuit 120, a drive signalprocessing circuit 121, and an image signal processing circuit 122.

The control circuit 120 controls an operation of writing a data signalto the liquid crystal display elements 108R, 108G, and 108B, a lightpath shifting operation in the light path shifting device 2, anoperation of generating the data signal in the image signal processingcircuit 122, and so on. The drive signal processing circuit 121 is adrive circuit for supplying drive signals DS to the light path shiftingdevice 2 based on a sync signal SA output by the image signal processingcircuit 122. A configuration including the drive signal processingcircuit 121 and the light path shifting device 2 combined with eachother corresponds to an example of an optical system.

The image signal processing circuit 122 separates an image signal Vidsupplied from an external device not shown into those for the threeprimary colors of R, G, and B, and at the same time, converts the resultinto data signals Rv, Gv, and By suitable to the operations of therespective liquid crystal display elements 108R, 108G, and 108B. Then,the data signals Rv, Gv, and By thus obtained by the conversion aresupplied respectively to the liquid crystal display elements 108R, 108G,and 108B, and the liquid crystal display elements 108R, 108G, and 108Bdraw the image based on the data signals Rv, Gv, and Bv, respectively.The light emitted by the light source 102 is dispersed into the redlight (R), the green light (G), and the blue light (B) as describedabove, and the colored light beams are modulated in accordance with theimages drawn in the liquid crystal display elements 108R, 108G, and108B, respectively.

The light path shifting device 2 is provided with the first actuator 6and the second actuator 7 as drive sources for driving the glass plate30. The drive signal processing circuit 121 outputs the drive signals DSto the first actuator 6 and the second actuator 7. The drive signals DSinclude a first drive signal DS1 for driving the first actuator 6 and asecond drive signal DS2 for driving the second actuator 7. To the firstactuator 6, there is input the first drive signal DS1, and to the secondactuator 7, there is input the second drive signal DS2.

4. Configuration of Liquid Crystal Display Element

FIG. 4 is a plan view showing a configuration of the liquid crystaldisplay element 108R. Since the liquid crystal display elements 108R,108G, and 108B all have a common configuration, the illustration and thedescription of the liquid crystal display element 108G and the liquidcrystal display element 108B will be omitted.

The liquid crystal display element 108R has a transmissive liquidcrystal display panel 181R. The liquid crystal display panel 181R is aliquid crystal panel for modulating the red light (R). The liquidcrystal display panel 181R is fitted into a frame 182, and is coupled toa drive circuit not shown.

The frame 182 is supported by a bracket 183. The bracket 183 is a jigfor fixing the frame 182 to a base member 184. The position where thebracket 183 is fixed to the base member 184 is adjustable, and byadjusting the attachment position of the bracket 183, it is possible toadjust the position of the liquid crystal display panel 181R.

The liquid crystal display panel 181R has a display area 180R fordisplaying an image. The display area 180R is an area where the image isformed in the liquid crystal display panel 181R, and the red light (R)obtained by dispersing the light emitted by the light source 102 istransmitted through the display area 180R to thereby be modulated. Inthe present embodiment, the display area 180R having a rectangular shapeis formed in the liquid crystal display panel 181R. Therefore, the imagelight modulated by the liquid crystal display element 108R istransmitted through the display area 180R having the rectangular shapeto turn to light forming the projection image 101A having therectangular shape.

FIG. 4 illustrates an axis AX and an axis AY in the display area 180R.The axes AX, AY are each an imaginary axis line. The axis AX is parallelto the X axis in the display area 180R, and the axis AY is parallel tothe Y axis in the display area 180R.

As described above, similarly to the liquid crystal display element108R, in the liquid crystal display elements 108G, 108B, images areformed in respective display areas not shown. The shape of the displayarea, and the correspondence between the display area and the X and Yaxes are common to the display area 180R.

5. Configuration of Light Path Shifting Device

FIG. 5 is a plan view of the light path shifting device 2. FIG. 6 is apartial cross-sectional view of the light path shifting device 2. FIG. 7is a partial enlarged cross-sectional view of the light path shiftingdevice 2.

The light path shifting device 2 has the glass plate 30, and the glassplate 30 is supported by a first frame 31. The first frame 31 is amember which is made of metal or synthetic resin, and which has aframe-like shape.

The glass plate 30 is a light transmissive substrate having a lighttransmissive property, and is an optical member which the image light LLenters. As shown in FIG. 4 , a red component of the image light LL istransmitted through the display area 180R to thereby be modulated intolight forming an image having a rectangular shape. The same applies to agreen component and a blue component of the image light LL. Therefore,the image light LL entering the glass plate 30 is transmitted through anoptical area 30A having a rectangular shape in the glass plate 30. Thecenter CE of the optical area 30A is a centroid in the plan view of thearea where the image light LL is transmitted at the reference position.In the present embodiment, the center CE of the optical area 30Acoincides with the center of the glass plate 30. The center CE can be aposition at which the central axis of the image light LL emitted fromthe glass plate 30 and the glass plate 30 cross each other.

It is sufficient for the glass plate 30 to have a size and a shapeincluding at least the optical area 30A, and it is possible for theplanar shape of the glass plate 30 to be a circular shape or a varietyof polygonal shapes including a rectangular shape.

It is preferable for an optical member provided to the light pathshifting device 2 to substantially be colorless and transparent. In thepresent embodiment, an example of using the glass plate 30 as an exampleof the optical member will be described. As the glass plate 30, therecan be used a variety of glass materials such as super white glass,borosilicate glass, or quartz glass. The optical member is only requiredto have a light transmissive property of transmitting the image lightLL, and can be formed of a variety of types of crystalline materialssuch as quartz crystal or sapphire, or a resin material such aspolycarbonate series resin or acrylic resin besides glass. When adoptingglass as the material of the optical member, since the rigidity of theoptical member is high, there is an advantage that it is possible tosuppress a variation in shift amount of the light path when shifting thelight path of the image light LL.

Further, in the glass plate 30, an antireflection film can be formed ona plane of incidence which the image light LL enters, and an exitsurface from which the image light LL is emitted.

FIG. 5 illustrates an axis BX and an axis BY respectively representingthe X direction and the Y direction in the optical area 30A of the glassplate 30. The axes BX, BY are imaginary axis lines corresponding to theaxes AX, AY in the display area 180R of the liquid crystal displayelement 108R and the display areas not shown of the liquid crystaldisplay elements 108G, 108B.

The light path shifting device 2 has the first axis J1 and the secondaxis J2. The first axis J1 and the second axis J2 are each an imaginaryaxis line forming the center of the rotation of the glass plate 30, andthe first axis J1 passes through the center CE of the optical area 30A.The second axis J2 passes through the center CE, and crosses the firstaxis J1. In the present embodiment, the first axis J1 and the secondaxis J2 bisect each other at right angles at the center CE.

The light path shifting device 2 is provided with a second frame 4 forswingably supporting the first frame 31, a base member 5 for swingablysupporting the second frame 4, and the first actuator 6 and the secondactuator 7 for displacing the glass plate 30.

The base member 5 is a ring-like member disposed so as to surround anoutside of the first frame 31. The second frame 4 is a ring-like member,and is disposed so as to surround the outside of the first frame 31. Thesecond frame 4 is housed in a groove not shown provided to the basemember 5.

The first frame 31 has protrusions 32, 33, 34, and 35 protruding inrespective directions corresponding to the four corners of the opticalarea 30A having the rectangular shape. The protrusions 32, 33 overlapthe second axis J2, and the protrusions 34, 35 are located at positionsoverlapping the first axis J1. The protrusion 32 is coupled to thesecond frame 4 via a support member 36. The protrusion 33 protrudes atan opposite side to the protrusion 32 with respect to the center CE ofthe optical area 30A. The protrusion 33 is coupled to the second frame 4via a support member 37.

The support members 36, 37 are disposed on the second axis J2. Thesupport member 36 has a shaft 36A connecting the second frame 4 and theprotrusion 32 to each other. The support member 37 has a shaft 37Aconnecting the second frame 4 and the protrusion 33 to each other. Theshafts 36A, 37A each have elasticity in a torsional direction. Thesupport member 36 and the support member 37 respectively support theboth ends of the first frame 31 in the second axis J2 direction. Thefirst frame 31 is supported by the second frame 4 with the shafts 36A,37A having elasticity so as to be able to rotate within a predeterminedrange centering on the second axis J2.

The protrusion 34 is located in a space 42 formed inside the secondframe 4, and can freely move. To the base member 5, there are fixedsupport members 45, 46 on the first axis J1. The support member 46 islocated at an opposite side to the support member 45 with respect to thecenter CE. Both ends of the second frame 4 on the first axis J1 aresupported by the base member 5 via the support member 45 and the supportmember 46.

The support member 45 has a shaft 45A connecting the second frame 4 andthe base member 5 to each other. The support member 46 has a shaft 46Aconnecting the second frame 4 and the base member 5 to each other. Theshafts 45A, 46A each have elasticity in a torsional direction. Thesecond frame 4 is supported by the base member 5 with the supportmembers 45, 46 so as to be able to rotate within a predetermined rangecentering on the first axis J1.

The glass plate 30 is swingable around the second axis J2 together withthe first frame 31, and is further swingably supported around the firstaxis J1 together with the second frame 4.

The first axis J1 and the second axis J2 bisect each other at rightangles, and the angle formed between the first axis J1 and a side of theoptical area 30A having the rectangular shape is smaller than 90°, andthe angle θ shown in the drawing is, for example, 45°. Therefore, theglass plate 30 in the present embodiment is supported so as to be ableto oscillate in two directions parallel to none of the sides of theoptical area 30A centering on the center CE. The oscillation directionsof the glass plate 30 are preferably directions parallel to none of thesides of the optical area 30A, the axis BX, and the axis BY, and aremore preferably directions having a tilt smaller than 90° with respectto the axis BX and the axis BY, respectively. As a most preferableexample, the oscillation directions of the glass plate 30 each coincidewith any of the directions of the first position P1, the second positionP2, the third position P3, and the fourth position P4 with respect tothe position P0 of the pixel Px shown in FIG. 2 . Specifically, theoscillation directions of the glass plate 30 are directions at an angleof 45° with both of the axis BX and the axis BY.

The first actuator 6 is disposed between one end of the second frame 4and the base member 5 on the second axis J2. The other end of the secondframe 4 on the second axis J2 is fitted into a cutout 51 provided to thebase member 5, and can freely move. It should be noted that the firstactuator 6 is not required to overlap the second axis J2.

The first actuator 6 is a vibratory actuator having a magnet 61, a coil62, a magnet holding plate 63, and a coil holding plate 64.

The magnet holding plate 63 is fixed to the second frame 4. The coilholding plate 64 is fixed to the base member 5. The magnet 61 isattached to the magnet holding plate 63, and the coil 62 is held by thecoil holding plate 64 at a position opposed to the magnet 61. The magnet61 and the coil 62 are not coupled to each other. Between the magnet 61and the coil 62, there is disposed a gap to the extent that the magnet61 and the coil 62 can move relatively to each other.

The second actuator 7 is disposed between the protrusion 35 and thesecond frame 4 on the first axis J1. The protrusion 34 located at anopposite side to the protrusion 35 is fit into the space 42 as describedabove, and can freely move. It should be noted that the second actuator7 is not required to overlap the first axis J1.

The second actuator 7 is a vibratory actuator having a magnet 71, a coil72, a magnet holding plate 73, and a coil holding plate 74.

The magnet holding plate 73 is fixed to the protrusion 35 of the firstframe 31. The coil holding plate 74 is fixed to the second frame 4. Themagnet 71 is attached to the magnet holding plate 73, and the coil 72 isheld by the coil holding plate 74 at a position opposed to the magnet71. The magnet 71 and the coil 72 are not coupled to each other. Betweenthe magnet 71 and the coil 72, there is disposed a gap to the extentthat the magnet 71 and the coil 72 can move relatively to each other.

FIG. 6 is a cross-sectional view of a principal part of the light pathshifting device 2 shown in FIG. 5 cut along the first axis J1. In FIG. 6and FIG. 7 described later, a normal direction of the glass plate 30when the glass plate 30 is located at the reference position isrepresented as the Z axis. The Z axis is perpendicular to each of thefirst axis J1 and the second axis J2. The image light LL enters theglass plate 30 along the Z axis.

In the second actuator 7, the magnet 71 and the coil 72 are disposed soas to be opposed to each other. The coil 72 is an air core coil havingan oval shape, and is provided with two effective sides 721, 722extending substantially in parallel to the second axis J2. The coil 72is positioned so that the two effective sides 721, 722 are arranged sideby side along the Z axis, and is then held by the coil holding plate 74.

A south pole 711 and a north pole 712 of the magnet 71 are arranged sideby side along the Z axis on an opposed surface opposed to the coil 72.The magnet 71 is a permanent magnet, and there can be used, for example,a neodymium magnet, a samarium-cobalt magnet, a ferrite magnet, and analnico magnet. When the glass plate 30 is located at the referenceposition, in the second actuator 7, one of the south pole 711 and thenorth pole 712 of the magnet 71 is opposed to the effective side 721,and the other thereof is opposed to the effective side 722.

When energizing the coil 72, the magnet 71 moves relatively to the coil72 along the Z axis. Thus, a driving force around the second axis J2 isapplied to the first frame 31 fixed to the magnet 71, and the firstframe 31 rotates around the second axis J2 together with the glass plate30.

The drive signal processing circuit 121 is capable of switching thedirection of the current flowing through the coil 72, namely thepolarity of the second drive signal DS2. In accordance with thedirection of the current flowing through the coil 72, the rotationaldirection of the first frame 31 changes. For example, in the case of theconfiguration in which the magnet 71 is displaced toward one side alongthe Z axis when the current flows in a forward direction through thecoil 72, when the current flows in an opposite direction through thecoil 72, the magnet 71 is displaced toward the other side along the Zaxis. Therefore, the second actuator 7 rotates the first frame 31 towardthe one side and the opposite side along the Z axis in accordance withthe polarity of the second drive signal DS2 input to the second actuator7 by the drive signal processing circuit 121.

FIG. 7 is a cross-sectional view of a principal part of the light pathshifting device 2 shown in FIG. 5 cut along the second axis J2, and inparticular, shows a configuration of the first actuator 6 and thevicinity thereof in an enlarged manner.

The magnet 61 and the coil 62 are disposed along the second axis J2 soas to be opposed to each other. The coil 62 is an air core coil havingan oval shape, and is provided with two effective sides 621, 622extending substantially in parallel to the first axis J1. The coil 62 ispositioned so that the two effective sides 621, 622 are arranged side byside along the Z axis, and is then fixed to the coil holding plate 64.

A south pole 611 and a north pole 612 of the magnet 61 are arranged sideby side along the Z axis on a surface opposed to the coil 62. The magnet61 is a permanent magnet, and there can be used a neodymium magnet, asamarium-cobalt magnet, a ferrite magnet, and an alnico magnet similarlyto the magnet 71. When the glass plate 30 is located at the referenceposition, in the first actuator 6, one of the south pole 611 and thenorth pole 612 of the magnet 61 is opposed to the effective side 621,and the other thereof is opposed to the effective side 622.

When energizing the coil 62, the magnet 61 moves relatively to the coil62 along the Z axis. Thus, a driving force around the first axis J1 isapplied to the second frame 4 which holds the magnet 61, and the secondframe 4 rotates around the first axis J1 together with the glass plate30.

The drive signal processing circuit 121 is capable of switching thedirection of the current flowing through the coil 62, namely thepolarity of the first drive signal DS1. In accordance with the directionof the current flowing through the coil 62, the rotational direction ofthe second frame 4 changes. For example, in the case of theconfiguration in which the magnet 61 is displaced toward one side alongthe Z axis when the current flows in a forward direction through thecoil 62, when the current flows in an opposite direction through thecoil 62, the magnet 61 is displaced toward the other side along the Zaxis. Therefore, the first actuator 6 rotates the second frame 4 towardthe one side and the opposite side along the Z axis in accordance withthe polarity of the first drive signal DS1 input to the first actuator 6by the drive signal processing circuit 121.

In the first actuator 6, the magnet holding plate 63 and the coilholding plate 64 are made of metal such as iron, and each function as aback yoke. Similarly in the second actuator 7, the magnet holding plate73 and the coil holding plate 74 are made of metal such as iron, andeach function as a back yoke. These back yokes exert an advantage ofdecreasing a leakage flux to increase magnetic efficiency.

By the incident angle of the image light LL to the glass plate 30 beingtilted from the reference position due to the actions of the firstactuator 6 and the second actuator 7, the glass plate 30 transmits theimage light LL having entered the glass plate 30 while refracting theimage light LL. Therefore, by changing the posture of the glass plate 30so as to achieve the target incident angle, it is possible to controlthe deflection direction and the deflection amount of the image lightLL.

FIG. 8 is an explanatory diagram showing a relative position between alight modulator 108 and the light path shifting device 2. FIG. 8 shows aconfiguration of the light modulator 108 so as to be superimposed on thecomponents of the light path shifting device 2 shown in FIG. 5 . FIG. 8shows the state of viewing the light path shifting device 2 and thelight modulator 108 from a position of the projection optical system 112on the light path of the image light LL.

The dichroic prism 110 is located at a position where the dichroic prism110 overlaps the glass plate 30 of the light path shifting device 2 inthe plan view along the Z axis, namely in the plan view of the glassplate 30. The liquid crystal display elements 108R, 108G, and 108B aredisposed so as to be opposed to the dichroic prism 110. The liquidcrystal display element 108G is located at the position where the liquidcrystal display element 108G overlaps the dichroic prism 110 and theglass plate 30 in the plan view of the glass plate 30, and the liquidcrystal display element 108R and the liquid crystal display element 108Bare located at the opposite sides along the BX axis with respect to thedichroic prism 110.

The liquid crystal display element 108R is attached to a liquid crystalframe 161R. The position of the liquid crystal display element 108G isat an opposite side to the glass plate 30 with respect to the dichroicprism 110.

Between the liquid crystal display element 108R and the dichroic prism110, there is disposed a polarization element 170R. The polarizationelement 170R is a rectangular optical member corresponding to the liquidcrystal display element 108R. The red light modulated by the liquidcrystal display element 108R is uniformed in polarization by thepolarization element 170R, and then enters the dichroic prism 110.

The polarization element 170R is attached with a polarization elementframe 171R surrounding the polarization element 170R, and thepolarization element frame 171R is fixed to the liquid crystal frame161R. Further, the liquid crystal display element 108R is attached witha fixation frame 172R surrounding the liquid crystal display element108R, and is fixed to the liquid crystal frame 161R via the fixationframe 172R.

The liquid crystal display element 108R and the polarization element170R are held by the polarization element frame 171R and the fixationframe 172R at appropriate positions with respect to the dichroic prism110.

The liquid crystal display element 108B is attached to a liquid crystalframe 161B.

Between the liquid crystal display element 108B and the dichroic prism110, there is disposed a polarization element 170B. The polarizationelement 170B is a rectangular optical member corresponding to the liquidcrystal display element 108B. The blue light modulated by the liquidcrystal display element 108B is uniformed in polarization by thepolarization element 170B, and then enters the dichroic prism 110.

The polarization element 170B is attached with a polarization elementframe 171B surrounding the polarization element 170B, and thepolarization element frame 171B is fixed to the liquid crystal frame161B. Further, the liquid crystal display element 108B is attached witha fixation frame 172B surrounding the liquid crystal display element108B, and is fixed to the liquid crystal frame 161B via the fixationframe 172B.

The liquid crystal display element 108B and the polarization element170B are held by the polarization element frame 171B and the fixationframe 172B at appropriate positions with respect to the dichroic prism110.

Further, although not shown in the drawings, similarly to the liquidcrystal display element 108R and the liquid crystal display element108B, the liquid crystal display element 108G is coupled to apolarization element 170G, and is fixed at an appropriate position withrespect to the dichroic prism 110.

The liquid crystal frames 161R, 161B, the polarization element frames171R, 171B, and the fixation frames 172R, 172B have the rigidity withwhich the liquid crystal display elements 108R, 108B and thepolarization elements 170R, 170B can surely be fixed. At least some ofthe liquid crystal frames 161R, 161B, the polarization element frames171R, 171B, and the fixation frames 172R, 172B constitute fixationmembers. These fixation members are desired to have a configurationhaving high rigidity and capable of suppressing the weight, and aretherefore preferably made of metal. In contrast, when making thefixation members from metal, an influence on the magnetic force of thefirst actuator 6 and the second actuator 7 of the light path shiftingdevice 2 is concerned. It should be noted that a fixation member for theliquid crystal display element 108G is longer in distance from the lightpath shifting device 2 than the liquid crystal display elements 108R,108B, and therefore has no influence on the first actuator 6 and thesecond actuator 7.

As shown in FIG. 8 , in the present embodiment, the first actuator 6 andthe second actuator 7 are disposed on the corners of the light pathshifting device 2. In particular, the first actuator 6 is disposed atthe end of the second frame 4 in the direction along the second axis J2,and the second actuator 7 is disposed at the end of the first frame 31in the direction along the first axis J1. Therefore, in a planeincluding the glass plate 30, the first actuator 6 and the secondactuator 7 are located at positions farther from the glass plate 30compared when the first actuator 6 and the second actuator 7 arerespectively located on the sides of the first frame 31 and the secondframe 4. When the first actuator 6 and the second actuator 7 aresupposedly located on these sides, there is a possibility that the firstactuator 6 and the second actuator 7 are opposed to the fixationmembers. It is possible to dispose the first actuator 6 or the secondactuator 7 and the fixation members at positions where these are notopposed to each other by making the length along the X axis of the wholeof the light path shifting device 2 sufficiently long, but the whole ofthe apparatus grows in size.

In contrast, when the first actuator 6 and the second actuator 7 aredisposed on the corners of the light path shifting device 2, even whenthe light path shifting device 2 has a size with which the side of thelight path shifting device 2 and the fixation member overlap each otherin the plan view, the first actuator 6 and the second actuator 7 locatedon the corners do not overlap the fixation member as long as thedistance between the first actuator 6 and the second actuator 7 islonger than the length of the fixation member. Therefore, the concernabout the mutual influence between the magnetic force of the firstactuator 6 and the second actuator 7, and the variety of metal membersdisposed on the periphery of the dichroic prism 110 is resolved.

6. Method of Driving Light Path Shifting Device

The light path shifting device 2 oscillates the glass plate 30 in twodirections, namely a first oscillation direction around the first axisJ1 and a second oscillation direction around the second axis J2, usingthe drive signals DS to be supplied from the drive signal processingcircuit 121. In the first actuator 6, a current flows through the coil62 based on the first drive signal DS1 input from the drive signalprocessing circuit 121, and thus, the magnet 61 is displaced. In thesecond actuator 7, a current flows through the coil 72 based on thesecond drive signal DS2, and thus, the magnet 71 is displaced.

FIGS. 9A to 9C are timing charts showing waveforms of the drive signalsDS and changes of the position of the pixel Px. In the timing chartshown in FIGS. 9A to 9C, FIG. 9A represents the waveform of the firstdrive signal DS1, FIG. 9B represents the waveform of the second drivesignal DS2, and FIG. 9C represents the position of the pixel Px. Thereference symbols t1 through t9 each represent a specific time. Thereference symbols PA, PB, PC, and PD shown in FIG. 9C indicate theimages displayed by the pixel Px. The images PA, PB, PC, and PD are theimages displayed at the first position P1, the third position P3, thefourth position P4, and the second position P2 shown in FIG. 2 ,respectively.

FIGS. 9A and 9B show a signal level A of the first drive signal DS1, anda signal level B of the second drive signal DS2.

In this example, the projector 1 displays the images in the order of theimages PB, PD, PC, and PA. The direction in which the light pathshifting device 2 moves the light path changes in the order of the thirddirection F3, the second direction F2, the fourth direction F4, and thefirst direction F1. The first drive signal DS1 and the second drivesignal DS2 each change between a positive signal level, a negativesignal level, and a level of 0. Therefore, the current values of thefirst drive signal DS1 and the second drive signal DS2 each changebetween a positive value, a negative value, and 0. Each of the signallevel of the first drive signal DS1 and the signal level of the seconddrive signal DS2 can be reworded as a value.

The first actuator 6 rotates the glass plate 30 in the normal directionaround the first axis J1 when the first drive signal DS1 has thepositive value, and rotates the glass plate 30 in the reverse directionaround the first axis J1 when the first drive signal DS1 has thenegative value. The second actuator 7 rotates the glass plate 30 in thenormal direction around the second axis J2 when the second drive signalDS2 has the positive value, and rotates the glass plate 30 in thereverse direction around the second axis J2 when the second drive signalDS2 has the negative value.

The state of the signal level A=0 of the first drive signal DS1corresponds to the state in which the first drive signal DS1 does notsubstantially excite the first actuator 6. In this state, the signallevel A is not required to completely vanish. Further, in a period ofthe signal level A=0, the signal level A can be 0. Further, in theperiod of the signal level A=0, it is possible to create the state inwhich the magnetic force of the first actuator 6 is in the level of notdisplacing the glass plate 30, and the signal level A is not 0. In otherwords, it is possible to create the state in which the displacement ofthe glass plate 30 does not substantially occur, and the signal level Ais not 0.

Similarly, the state of the signal level B=0 of the second drive signalDS2 corresponds to the state in which the second drive signal DS2 doesnot substantially excite the second actuator 7. In this state, thesignal level B is not required to completely vanish. In a period of thesignal level B=0, the signal level B can be 0. Further, in the state ofthe signal level B=0, it is possible to create the state in which themagnetic force of the second actuator 7 is in the level of notdisplacing the glass plate 30, and the signal level B is not 0. In otherwords, it is possible to create the state in which the displacement ofthe glass plate 30 does not substantially occur, and the signal level Bis not 0.

The value a1 of the signal level A is a predetermined positive value,and the value a2 is a predetermined negative value. The value b1 of thesignal level B is a predetermined positive value, and the value b2 is apredetermined negative value.

In FIGS. 9A to 9C, the first drive signal DS1 rises in a period from thebeginning of the action to the time t1, and thus, the signal level Areaches the value a1. When the signal level A of the first drive signalDS1 is positive, and the signal level B of the second drive signal DS2is 0, the light path shifting device 2 shifts the light path toward thethird direction F3 shown in FIG. 2 . Thus, the projector 1 displays theimage PB.

In a period from the time t2 to the time t3, the first drive signal DS1falls, and at the same time, the second drive signal DS2 rises, andthus, the signal level A reaches 0, and the signal level B reaches thevalue b1. The light path shifting device 2 shifts the light path towardthe second direction F2 shown in FIG. 2 when the signal level B ispositive, and the signal level A is 0. Thus, the projector 1 displaysthe image PD.

In a period from the time t4 to the time t5, the first drive signal DS1falls, and at the same time, the second drive signal DS2 falls, andthus, the signal level A reaches the value a2, and the signal level Breaches 0. The light path shifting device 2 shifts the light path towardthe fourth direction F4 shown in FIG. 2 when the signal level A isnegative, and the signal level B is 0. Thus, the projector 1 displaysthe image PC.

In a period from the time t6 to the time t7, the first drive signal DS1rises, and at the same time, the second drive signal DS2 falls, andthus, the signal level A reaches 0, and the signal level B reaches thevalue b2. The light path shifting device 2 shifts the light path towardthe first direction F1 shown in FIG. 2 when the signal level B isnegative, and the signal level A is 0. Thus, the projector 1 displaysthe image PA.

In a period from the time t8 to the time t9, the first drive signal DS1rises, and at the same time, the second drive signal DS2 rises, and thesignal level A reaches the value a1, and the signal level B reaches 0.Thus, the projector 1 displays the image PB.

The light path shifting device 2 shifts the light path toward the thirddirection F3 and the fourth direction F4 with the first actuator 6.Further, the light path is shifted toward the first direction F1 and thesecond direction F2 with the second actuator 7. In other words, in theprocess of shifting the light path toward the four directions, namelythe first direction F1 through the fourth direction F4, the state inwhich the first actuator 6 and the second actuator 7 are excited at thesame time is not required.

Therefore, as shown in FIGS. 9A to 9C, in the period of displaying theimage, since a period in which the signal level A and the signal level Bare kept at positive values at the same time, and a period in which thesignal level A and the signal level B are kept at negative values at thesame time do not exist, it is possible to suppress the current values ofthe drive signals DS output by the drive signal processing circuit 121,and it is possible to suppress the consumption of the power for drivingthe light path shifting device 2.

Further, as shown in the period between t2 and t3, the period between t4and t5, and so on, when the direction in which the light path is shiftedis switched, it is possible to make the first actuator 6 and the secondactuator 7 individually operate. Specifically, it is possible for therising timing or the falling timing of the first drive signal DS1 andthe rising timing or the falling timing of the second drive signal DS2to overlap each other. Therefore, it is possible to switch the shiftdirection of the light path in a short time.

In order to prevent the projection image 101A from becoming unclear, itis desirable not to display the image during a period of switching theshift direction of the light path. As shown in FIGS. 9A to 9C, since thelight path shifting device 2 is capable of switching the shift directionof the light path in a short time, a period in which the image is notdisplayed is short, and the proportion of a period in which the imagecan be displayed is high. Thus, it is possible to project the projectionimage 101A high in resolution feeling and high in display quality.

As described hereinabove, in the method of driving the light pathshifting device 2, the light path shifting device 2 includes the glassplate 30 having the optical area 30A which has a rectangular shape inplan view, and which the light enters, the first actuator 6, and thesecond actuator 7. The first actuator 6 displaces the glass plate 30around the first axis J1 which passes through the center CE of theoptical area 30A in the plan view, and which forms an angle smaller than90° with the first side of the optical area 30A. The second actuator 7displaces the glass plate 30 around the second axis J2 which passesthrough the center CE of the optical area 30A, and which isperpendicular to the first axis J1. The method of driving the light pathshifting device 2 includes the steps of inputting the first drive signalDS1 into the first actuator 6 to thereby excite the first actuator 6,inputting the second drive signal DS2 into the second actuator 7 tothereby excite the second actuator 7, and setting the value of thesecond drive signal DS2 to a value for substantially stopping theexcitation of the second actuator 7 in the period of exciting the firstactuator 6.

In the light path shifting device 2, by making the first actuator 6operate, it is possible to oscillate the glass plate 30 around the firstaxis J1 which forms an angle smaller than 90° with the first side of theoptical area 30A. Further, by making the second actuator 7 operate, itis possible to oscillate the glass plate 30 around the second axis J2perpendicular to the first axis J1.

It is possible for the method of driving the light path shifting device2 to shift the image light LL in a plurality of directions differentfrom each other, and nonparallel to the sides of the optical area 30A bymaking either one of the first actuator 6 and the second actuator 7operate. In this drive method, when driving the light path shiftingdevice 2, the excitation of the second actuator 7 is substantiallystopped during the period of exciting the first actuator 6. For example,in the drive method shown in FIGS. 9A to 9C, in the period between t1and t2 and the period between t5 and t6, while exciting the firstactuator 6 with the first drive signal DS1, the signal level of thesecond drive signal DS2 is 0, and thus, the second actuator 7 issubstantially stopped. Thus, the operation of shifting the image lightLL to make the display image high-resolution can be performed with lowpower consumption.

The drive method described above includes the steps of exciting thesecond actuator 7 with the second drive signal DS2, and setting thevalue of the first drive signal DS1 to a value for substantiallystopping the excitation of the first actuator 6 in the period ofexciting the second actuator 7.

For example, in the period between t3 and t4 and the period between t7and t8, while the second drive signal DS2 is in the state of excitingthe second actuator 7, the signal level of the first drive signal DS1 is0, and thus, the excitation of the first actuator 6 is substantiallystopped. Thus, the operation of shifting the image light LL to make thedisplay image high-resolution can be performed with low powerconsumption.

In the drive method described above, assuming the value of the seconddrive signal DS2 as B, the value for stopping the excitation of thesecond actuator 7 includes B=0. In this case, by setting the value B ofthe second drive signal DS2 to B=0, it is possible to surely set theexcitation of the second actuator 7 to the state of being substantiallystopped, and it is possible to further reduce the power consumption ofthe light path shifting device 2.

The drive method described above includes a first period in which B=b1is set and a second period in which B=b2 is set defining the value ofthe second drive signal DS2 as B, and assuming the value b1 as aconstant satisfying b1>0 and the value b2 as a constant satisfying b2<0.For example, in FIGS. 9A to 9C, the period between t3 and t4 is anexample of a first period, and the period between t7 and t8 is anexample of a second period. In these periods, by setting the value A ofthe first drive signal DS1 to the value for substantially stopping theexcitation of the first actuator 6, it is possible to further reduce thepower consumption of the light path shifting device 2.

The drive method described above includes either one of a third periodin which A>0 and B=0 are set and a fourth period in which A<0 and B=0are set between the first period and the second period defining thevalue of the first drive signal DS1 as A. For example, in FIGS. 9A to9C, the period between t5 and t6 is an example of the fourth period.Further, when performing the same operation started at the time t9 asthe operation started at the time t1 and subsequent times, it ispossible to include the period of the time t1 through the time t2 inwhich A>0 and B=0 are set following the period between t7 and t8corresponding to the second period. In this case, the period between t1and t2 corresponds to an example of the third period. In these periods,by setting either of the values of the first drive signal DS1 and thesecond drive signal DS2 to the value for substantially stopping theexcitation of the actuator, it is possible to further reduce the powerconsumption of the light path shifting device 2.

In the drive method described above, assuming the value a1 as a constantsatisfying a1>0, and the value a2 as a constant satisfying a2<0, it ispossible to set A=a1 in the third period, and A=a2 in the fourth period.As described above, the period between t1 and t2 corresponds to anexample of the third period, and the period between t5 and t6corresponds to an example of the fourth period. In these periods, byexciting the first actuator 6 with the first drive signal DS1, andsubstantially stopping the excitation of the second actuator 7, it ispossible to further reduce the power consumption of the light pathshifting device 2.

The drive method described above includes a fifth period in which thevalue A of the first drive signal DS1 and the value B of the seconddrive signal DS2 change between the first period and the third period,or between the first period and the fourth period. For example, in FIGS.9A to 9C, in the period between t2 and t3, the period between t4 and t5,the period between t6 and t7, and the period between t8 and t9, thevalues of the first drive signal DS1 and the second drive signal DS2change. These periods each correspond to an example of the fifth period.According to this drive method, by changing the value of the first drivesignal DS1 and the value of the second drive signal DS2 at the sametime, it is possible to complete the operation of shifting the imagelight LL in a short time.

For example, it is possible for the light path shifting device 2 tooscillate the glass plate 30 together with the second frame 4 by makingthe second actuator 7 operate, and to oscillate the glass plate 30together with the first frame 31 to operate the first actuator 6.According to this configuration, since there is no chance for the actionof the first actuator 6 and the action of the second actuator 7 tointerfere with each other, the operation of making the first actuator 6and the second actuator 7 act at the same time to shift the image lightLL can be completed in a short time. Therefore, there is an advantagethat it is possible to move the glass plate 30 in a short time, and evenwhen stopping the display while the glass plate 30 is moving, theresolution feeling of the projection image 101A is not damaged.

In the drive method described above, the light path shifting device 2makes the glass plate 30 guide the incident light to the second positionP2 in the first period, and makes the glass plate 30 guide the incidentlight to the third position P3 in the third period. Further, the lightpath shifting device 2 makes the glass plate 30 guide the incident lightto the fourth position P4 in the fourth period, and makes the glassplate 30 guide the incident light to the first position P1 in the secondperiod.

According to this method, the image light LL is guided to the respectivepositions different from each other in the first period of setting B=b1and A=0, the second period of setting B=b2 and A=0, the third period ofsetting A>0 and B=0, and the fourth period of setting A<0 and B=0.Therefore, it is possible to shift the image light LL to the fourdifferent positions by exciting the first actuator 6 and the secondactuator 7 substantially one by one, and thus, it is possible to realizethe high resolution of the projection image 101A with lower powerconsumption.

The optical system obtained by combining the drive signal processingcircuit 121 with the light path shifting device 2 is provided with thelight path shifting device 2 including the glass plate 30, the firstactuator 6, and the second actuator 7, and the drive signal processingcircuit 121. In the glass plate 30, the light enters the optical area30A having a rectangular shape in the plan view. The first actuator 6displaces the glass plate 30 around the first axis J1 which passesthrough the center CE of the optical area 30A in the plan view, andwhich forms an angle smaller than 90° with the first side of the opticalarea 30A. The second actuator 7 displaces the glass plate 30 around thesecond axis J2 which passes through the center CE of the optical area30A, and which is perpendicular to the first axis J1. The drive signalprocessing circuit 121 executes the steps of outputting the first drivesignal DS1 to the first actuator 6 to thereby excite the first actuator6, outputting the second drive signal DS2 to the second actuator 7 tothereby excite the second actuator 7, and setting the value of thesecond drive signal DS2 to the value for substantially stopping theexcitation of the second actuator 7 during the period of exciting thefirst actuator 6.

The projector 1 is provided with the light source 102, and the lightmodulator 108 for modulating the light emitted from the light source102. The projector 1 is provided with the light path shifting device 2including the glass plate 30, the first actuator 6, and the secondactuator 7, the drive signal processing circuit 121, and the projectionoptical system 112. In the glass plate 30, the light modulated by thelight modulator 108 enters the optical area 30A having a rectangularshape in the plan view. The first actuator 6 displaces the glass plate30 around the first axis J1 which passes through the center CE of theoptical area 30A in the plan view, and which forms an angle smaller than90° with the first side of the optical area 30A. The second actuator 7displaces the glass plate 30 around the second axis J2 which passesthrough the center CE of the optical area 30A, and which isperpendicular to the first axis J1. The drive signal processing circuit121 executes the steps of outputting the first drive signal DS1 to thefirst actuator 6 to thereby excite the first actuator 6, outputting thesecond drive signal DS2 to the second actuator 7 to thereby excite thesecond actuator 7, and setting the value of the second drive signal DS2to the value for substantially stopping the excitation of the secondactuator 7 during the period of exciting the first actuator 6.

In the light path shifting device 2, by making the first actuator 6operate, it is possible to oscillate the glass plate 30 around the firstaxis J1 which forms an angle smaller than 90° with the first side of theoptical area 30A. Further, by making the second actuator 7 operate, itis possible to oscillate the glass plate 30 around the second axis J2perpendicular to the first axis J1.

According to the optical system and the projector 1 described above, itis possible to shift the image light LL in a plurality of directionsdifferent from each other, and nonparallel to the sides of the opticalarea 30A by making either one of the first actuator 6 and the secondactuator 7 operate. When driving the light path shifting device 2, theexcitation of the second actuator 7 is substantially stopped during theperiod of exciting the first actuator 6. For example, in FIGS. 9A to 9C,in the period between t1 and t2 and the period between t5 and t6, whileexciting the first actuator 6 with the first drive signal DS1, the valueof the second drive signal DS2 is 0, and thus, the excitation of thesecond actuator 7 is substantially stopped. Thus, the operation ofshifting the image light LL to make the display image high-resolutioncan be performed with low power consumption.

7. Other Embodiments

The embodiment described above is a preferred embodiment of the presentdisclosure. It should be noted that the present disclosure is notlimited to the embodiment described above, but can be implemented with avariety of modifications within the scope or the spirit of the presentdisclosure.

For example, the description is presented assuming that the firstactuator 6 has the configuration in which the magnet 61 is fixed to thesecond frame 4, the coil 62 is fixed to the base member 5, and thesecond frame 4 is displaced together with the magnet 61 by energizingthe coil 62, but this is illustrative only. As a modified example, it ispossible to adopt a configuration in which the coil 62 is fixed to thesecond frame 4, the magnet 61 is fixed to the base member 5, and thesecond frame 4 is displaced by energizing the coil 62. Similarly, thedescription is presented assuming that the second actuator 7 has theconfiguration in which the magnet 71 is fixed to the first frame 31, thecoil 72 is fixed to the second frame 4, and the first frame 31 isdisplaced together with the magnet 71 by energizing the coil 72, butthis is illustrative only. As a modified example, it is possible toadopt a configuration in which the coil 72 is fixed to the first frame31, the magnet 71 is fixed to the second frame 4, and the first frame 31is displaced by energizing the coil 72.

Further, in the embodiment described above, there is described theconfiguration of using the vibratory actuator which makes the magnet andthe coil be opposed to each other to generate the drive force as aLorentz force as the first actuator 6 and the second actuator 7. Thepresent disclosure is not limited thereto, and it is possible to use anactuator which operates on another principle. It is possible to adopt,for example, a piezo actuator.

In the embodiment described above, it is possible for the projector 1 tohave a configuration provided with a sensor for detecting the directionof the displacement and the amount of the displacement of the glassplate 30. In this case, it is possible for the control circuit 120 to beprovided with a function of correcting the drive signals DS based on thedetection result of the sensor.

The waveforms of the first drive signal DS1 and the second drive signalDS2 illustrated in FIGS. 9A and 9C are a typical example, and are notintended to limit the actual signal waveforms to those coinciding withFIGS. 9A to 9C. Further, the explanatory diagram of the optical systemshown in FIG. 1 and the functional block diagram shown in FIG. 3 are thediagrams schematically showing the configuration example of theprojector 1, but do not limit the target apparatus to which the presentdisclosure is applied.

What is claimed is:
 1. A method of driving an optical device comprising:an optical device including an optical member having an optical area onwhich light incidents, the optical area having a rectangular shape in aplan view, a first actuator configured to displace the optical memberaround a first axis which passes through a center of the optical area inthe plan view, and the first axis forms an angle smaller than 90° with afirst side of the optical area, and a second actuator configured todisplace the optical member around a second axis which passes throughthe center of the optical area, and the second axis is perpendicular tothe first axis, the method including: exciting the first actuator byinputting a first drive signal to the first actuator; exciting thesecond actuator by inputting a second drive signal to the secondactuator; and setting a value of the second drive signal to a value forsubstantially stopping exciting the second actuator in a period of theexciting the first actuator.
 2. The method of driving the optical deviceaccording to claim 1, further comprising: setting a value of the firstdrive signal to a value for substantially stopping exciting the firstactuator in a period of the exciting the second actuator.
 3. The methodof driving the optical device according to claim 1, wherein the valuefor stopping exciting the second actuator includes B=0, where B is thevalue of the second drive signal.
 4. The method of driving the opticaldevice according to claim 1, wherein the exciting the second actuatorincludes a first period in which B=b1, and a second period in whichB=b2, where B is the value of the second drive signal, b1 is a constantsatisfying b1>0, and b2 is a constant satisfying b2<0.
 5. The method ofdriving the optical device according to claim 4, wherein the setting thevalue of the second drive signal includes one of a third period in whichA>0 and B=0, and a fourth period in which A<0 and B=0 between the firstperiod and the second period, where A is a value of the first drivesignal.
 6. The method of driving the optical device according to claim5, wherein assuming a1 as a constant satisfying a1>0, and a2 as aconstant satisfying a2<0, A=a1 in the third period, and A=a2 in thefourth period, where a1 is a constant satisfying a1>0, and a2 is aconstant satisfying a2<0.
 7. The method of driving the optical deviceaccording to claim 5, wherein the value A and the value B change betweenthe first period and the third period, or between the first period andthe fourth period.
 8. An optical system comprising: an optical deviceincluding an optical member having an optical area on which lightincidents, the optical area having a rectangular shape in a plan view, afirst actuator configured to displace the optical member around a firstaxis which passes through a center of the optical area in the plan view,and the first axis forms an angle smaller than 90° with a first side ofthe optical area, and a second actuator configured to displace theoptical member around a second axis which passes through the center ofthe optical area, and the second axis is perpendicular to the firstaxis; and a drive circuit configured to perform exciting the firstactuator by outputting a first drive signal to the first actuator,exciting the second actuator by outputting a second drive signal to thesecond actuator, and setting a value of the second drive signal to avalue for substantially stopping exciting the second actuator in aperiod of the exciting the first actuator.
 9. A display comprising: alight source; a light modulator configured to modulate light emittedfrom the light source; an optical device including an optical memberhaving an optical area on which light modulated by the light modulatorincidents, the optical area having a rectangular shape in a plan view, afirst actuator configured to displace the optical member around a firstaxis which passes through a center of the optical area in the plan view,and the first axis forms an angle smaller than 90° with a first side ofthe optical area, and a second actuator configured to displace theoptical member around a second axis which passes through the center ofthe optical area, and the second axis is perpendicular to the firstaxis; a drive circuit; configured to perform exciting the first actuatorby outputting a first drive signal to the first actuator, exciting thesecond actuator by outputting a second drive signal to the secondactuator, and setting a value of the second drive signal to a value forsubstantially stopping exciting the second actuator in a period of theexciting the first actuator; and an optical system configured totransmit the light transmitted through the optical device.